1. Field of the Invention
The present invention relates to a method and apparatus for cleaning waste gas generated from power generating machines, industrial facilities, incinerators, etc., and more particularly to a method and apparatus for reducing harmful ingredients contained in the waste gas by dissociating the ingredients by irradiation with gas laser and electron beams thereto.
2. Description of the Prior Art
Korean Patent Application Laid-Open No. 96-21112 discloses a conventional method and apparatus for treating waste gas by irradiation with electron beams. According to this method and apparatus, ammonia is added to the waste gas mainly containing sulfuric oxide (SOx) or nitrogen oxide (NOx), and then the sulfuric oxide and nitrogen oxide are changed to ammonium sulfate and ammonium nitrate by irradiation of electron beams thereto, so that the harmful ingredients, i.e., SOx and NOx, are eliminated from the exhaust gas. In such a method using ammonia gas for eliminating the harmful ingredients, however, the ammonia gas is apt to be exhausted together with the exhaust gas under an incomplete reaction of the above-described ingredients. Further, this method and apparatus has problems of necessitating a separate apparatus for mixing ammonia with the waste gas as well as uneven irradiation of electron beams into the waste gas.
U.S. Pat. No. 4,915,916 discloses a method and apparatus for treating waste gas by irradiation with electron beams without using ammonia. According to this method and apparatus, a part of the waste gas to be treated is irradiated with electron beams to form active species such as [O] and OHxe2x80x94 radicals, and the waste gas having the active species is dispersed into and mixed into the remaining waste gas to change NOx and SOx in the waste gas into the form of a mist or dust by the action of the active species. The mist or dust is then captured by a dust collector. However, this method and apparatus has problems such as a low efficiency of eliminating the harmful ingredients and a large size of the apparatus since the electron beam irradiation region is separated from the reaction region.
The conventional apparatuses and methods for treating harmful gas with electron beams as described above also have drawbacks such that the electron beam irradiation region does not cover the entire path of the waste gas, and a low density of electron beams results in a low speed and efficiency of eliminating the harmful ingredients.
An object of the present invention is to provide a method and apparatus for cleaning harmful gas which has a compact size and high efficiency by defining one region for both a gas laser and electron beam irradiation region, and an exhaust gas reaction region, and without the necessity of a separate intermediate material such as ammonium.
Another object of the present invention is to provide a method and apparatus for cleaning harmful gas of a high treatment efficiency and speed by irradiating high-density gas laser and electron beams throughout the path of the harmful gas.
Still another object of the present invention is to provide a method and apparatus for generating a high-frequency and high voltage signal which can produce gas laser and electron beams conforming to the above objects.
In one aspect of the present invention, there is provided an apparatus for reducing harmful ingredients in gas by irradiating the gas with an electron beam, the apparatus comprising a voltage generating unit adapted to generate a high-frequency and high voltage signal, and a reaction unit coupled to the voltage generating unit to receive the high-frequency and high voltage signal, the reaction unit including an electron beam pole having a plurality of openings along the surface of the electron beam pole, and a plurality of discharge cells for each opening, the discharge cells being disposed to face the corresponding opening for generation of the electron beam therebetween, the region between the discharge cells and the openings defining a reaction region through which the gas travels.
In a preferred embodiment of the present invention, the electron beam pole has an annular shape and the openings are formed around the annular wall of the electron beam pole, and the discharge cells are stacked and each cell has an electrode tip pointing toward the corresponding opening.
In the preferred embodiment of the present invention, the electron beam pole has an annular shape, and the openings are elongated and disposed at a predetermined angle with respect to the radial axis of the electron beam pole, and the discharge cells are stacked and aligned along the corresponding elongated opening, and each cell has an electrode tip pointing toward the corresponding elongated opening.
Preferably, each discharge cell of the stacked discharge cells for each opening is radially offset from the adjacent discharge cell by a predefined angle in the range of 5xc2x0 to 20xc2x0.
According to the preferred embodiment, an energy power supply unit coupled to the voltage generator and the reaction unit to supply the high-frequency and high voltage signal to the electron beam pole, the energy power supply unit including a central frame secured to the electron beam pole, a case secured to the plurality of discharge cells and surrounding the central frame, and a coupling member coupling the central frame to the case. The coupling member comprises a central shaft secured to the electron beam pole, a pair of reinforcing shafts transversely secured to both ends of the central shaft, a plurality of insulator terminals attached to both ends of the reinforcing shafts and having outer surfaces secured to the case, and an energy input terminal, attached to an external surface of the case in an insulated state and connected to the central shaft in a conductive state, for supplying the high-frequency and high voltage signal from the voltage generation unit to the electron beam pole.
Preferably, the apparatus for cleaning harmful gas according to the present invention may further comprise a compressed air supply unit for supplying compressed air to the reaction region.
In another aspect of the present invention, there is provided a harmful gas cleaning method for reducing harmful ingredients in waste gas by irradiation with an electron beam, the method comprising the steps of converting an AC supply voltage to a high DC voltage, an oscillating high-frequency high voltage signal, and a high-frequency high voltage ring waveform signal, combining the high DC voltage, the oscillating high-frequency high voltage signal, and the high-frequency high voltage ring waveform signal to produce a final signal of high-frequency and high voltage, generating an electron beam by applying the final signal across a beam pole and discharge cells, and irradiating the electron beam against the waste gas passing through a reaction region defined by the area between the beam pole and the discharge cells.